1. Field of the Invention
The present invention relates to a living body information measuring apparatus and the like for noninvasively measuring a subject's living body information such as the pulse rate, the blood-sugar level, subject's subcutaneous fat thickness and fat percentage.
2. Related Art of the Invention
An apparatus for noninvasively measuring a subject's body fat percentage has previously been proposed.
For example, U.S. Pat. No. 4,990,772 proposes a method of measuring a subject's body fat percentage by use of near infrared rays. According to this United States Patent, near infrared rays used for ingredient analysis of food and the like are projected to a subject, and a specific wavelength component of the light having intruded into the subject is analyzed.
FIG. 45 shows the structure of a body fat percentage measuring apparatus according to the prior art. As shown in the figure, a pair of light emitting devices 12A and a light receiving device 13A are disposed on one end surface of a body 11A. In a cap 14A for protecting the end surface, an optical standard plate 15A is disposed so as to be opposed to the light emitting devices 12A and the light receiving device 13A. The light emitting devices 12A project near infrared rays to a subject being in intimate contact with the end surface of the body 11A. The projected light is reflected after intruding into the subject. The light receiving device 13A detects the reflected light. A microcomputer (not shown) incorporated in the body 11A calculates the subject's body fat percentage based on data on the subject's height and weight and the information on the reflected light detected by the light receiving device 13A. In the actual measurement, first, light projection and reflected light detection are performed with the cap 14A being fitted on the body 11A, and a reference value for the subsequent measurement is obtained. Thereafter, light projection to the subject and reflected light detection are performed.
However, in the above-described body fat measuring apparatus, light-shading is insufficient according to the subject's measured part such as an arm which is thin. Light-shading is also insufficient according to the angle at which the body fat measuring apparatus is pressed against the subject. Consequently, accurate data cannot be obtained.
Moreover, since it is necessary to perform measurement twice for adjustment and for actual measurement, a long time is required for the measurement.
Moreover, since the color of the skin differs among individuals, when the color of the skin is different among subjects, the body fat percentage detected by a body fat measuring apparatus that projects light from above the skin is naturally inaccurate.
Moreover, in the conventional body fat measuring apparatus, since near infrared rays (wavelength 950 nm) are used, when the measurement is performed at a very bright place, the light having propagated through the living body becomes a disturbance because of the property of near infrared rays of more excellently passing through living bodies than visible light, so that accurate measurement cannot be performed.
Moreover, since the conventional body fat measuring apparatus uses near infrared rays which is largely absorbed by fat component, when the subject persons have different fat quality, the amount of light becomes largely changed, and Then it is difficult to detect accurately the thickness of fat.
Moreover, since the intensity of the light source and the sensitivity of the light receiving portion vary with time, it is necessary to obtain the reference value for the subsequent measurement every measurement by projecting light with the cap being fitted on the body and detecting the reflected light from the standard plate, which is very cumbersome.
Moreover, when the optical standard plate becomes dirty for some reason, the measurement value significantly differs.